addresses issue #118
Addressing next page null values as per issue #118 @popwarfour
added constant for size of the page (default is 20)
added new constant, PAGE_SIZE, which is set to 20 by default. Replaced all instances of magic numbers in the datastore code with this constant
added command line argument support for spider testing script. This resolves issue #121
Added sorting to datastore comment return

Added a call to sort comments by timestamp to get validation tests
passing for #124
Merge commit '858aa6d' into develop